After spawning in the western Atlantic, millions of tiny eels make their way across thousands of miles of sea to Europe. But that's only the beginning of their journey – the fish then must find a suitable river and travel its length to find a desired area of wetlands, where they will spend decades before returning to their birthplace to die.
However, for many, death comes much earlier. Many of their habitats have been drained in recent decades and more than a million weirs and dams block their migratory routes. On top of that, eels are a major victim of organized crime, being worth more per kilo in international markets than smuggled cocaine.
Today, the once-common European Eel is critically endangered. But the fightback is under way – and fisherman and giant concrete structures have become unlikely allies of the eels.